Hyperacusis

What is Hyperacusis?

Hyperacusis is a condition that causes an increased sensitivity to everyday sounds. For people with hyperacusis, noises that wouldn't bother most individuals—like the sound of a car passing by, a dog barking or dishes clinking—can be extremely uncomfortable or even painful. This heightened sensitivity can make it difficult to engage in daily activities, leading to stress and social isolation.

Hyperacusis vs. Misophonia vs. Phonophobia

Hyperacusis is a heightened sensitivity to everyday sounds, often causing physical discomfort or pain. It’s related to how sounds are processed in the brain, not necessarily linked to any emotional reaction.

Misophonia is a strong emotional response to specific “trigger sounds,” which are typically human-originating sounds such as chewing, slurping, noisy breathing, tying on a keyboard, click of a pen, etc. Rather than pain, people with misophonia often feel anger, anxiety, or disgust when exposed to these sounds.

Phonophobia is the fear of certain sounds, where individuals might avoid environments or activities due to the anticipation of discomforting sounds. Phonophobia is often related to anxiety or past experiences and may overlap with hyperacusis.

Causes of Hyperacusis

Hyperacusis can have several potential causes, many of which are still unclear. Key causes include:

Sensorineural Hearing Loss: Damage to the hair cells of the cochlea (the sensory organ of hearing) will lead to a phenomenon called "cochlear recruitment", where those damaged hair cells amplify sounds excessively. As a result, sounds become uncomfortably loud much quicker than they would for someone with normal hearing. In a healthy ear, sound perception increases gradually with volume, but with in a damaged ear with cochlear recruitment, sounds shift from being barely audible to uncomfortably loud very quickly. In other words, there is no middle ground in sound intensity. This is what we call a reduced dynamic range. This sudden jump in loudness can lead to hyperacusis, where normal sounds feel painfully intense. Any cause of sensorineural hearing loss affecting the cochlea preferentially (instead of the hearing nerve) can trigger a recruitment phenomenon. Here are some examples:

• Noise-Induced Hearing Damage: Exposure to loud noises over time (like from concerts, machinery, or headphones) can alter hearing sensitivity, leading to hyperacusis.
• Ototoxicity from Medications: Certain medications, especially high doses of antibiotics or chemotherapy agents, may damage the inner ear and increase sound sensitivity.
• Presbycusis: hearing loss seen with aging.

Migraine-Related Hyperacusis: Migraines can impact the way the brain processes sensory input, including sound. This is a very common cause of hyperacusis. Not always associated with headaches.

Head or Ear Trauma: Injuries to the head or ear, such as concussions, can lead to changes in auditory processing. This is another common cause of hyperacusis.

Superior Canal Dehiscence Syndrome (SCDS): This rare condition, where there is a small opening (called dehiscence) in the bone covering the inner ear which leads to changes in the mechanics of the inner ear fluids, causing hyperacusis, sensitivity to body sounds (such as one’s heartbeat or even eye movements) and even vertigo with loud sounds. Can be surgically corrected.

Anxiety and Psychological Factors: Stress, anxiety, and other mental health conditions can amplify sound sensitivity, as heightened awareness may increase response to sounds.

Bell's palsy: When the facial nerve becomes paralyzed, as in Bell's palsy, it can result in hyperacusis. This occurs because the stapedius muscle in the middle ear, which helps to dampen sounds by stiffening the hearing bones, is unable to function properly. Fortunately, this condition is typically temporary and tends to resolve as the paralysis heals, which may take several months.

Other Conditions: Conditions like autism spectrum disorder and Williams syndrome may also be associated hyperacusis or related auditory symptoms.

How is Hyperacusis Diagnosed?

A thorough history and physical exam are crucial to understanding hyperacusis. History-taking will involve questions about the onset of sound sensitivity, specific sounds that trigger discomfort, lifestyle impacts, and possible exposure to loud noises or head trauma. The doctor may also ask about any recent infections, migraines, or mental health concerns.

During the physical examination, the ENT specialist will inspect the ears and may perform tests to check hearing sensitivity and look for physical abnormalities. Some exams might include maneuvers to evaluate for related conditions like superior canal dehiscence.

Work-Up for Hyperacusis

Diagnostic tests help determine the severity and nature of hyperacusis. Common tests include:

• Audiograms and High-Frequency Audiograms: These hearing tests can reveal any hearing loss patterns that may be related to hyperacusis.

• Metz Recruitment Test : Is a simple yet powerful tool we use in audiology to detect cochlear recruitment. This test is based on measuring something called the acoustic stapedius reflex. Here's how it works:

• • We have a tiny muscle in our middle ear called the stapedius muscle.
  • This muscle contracts when we hear loud sounds to protect our inner ear.
  • The Metz test measures when this muscle contracts in response to sound.
    
  
  When we perform the Metz test, we're looking at two key measurements

• • The patient's hearing threshold (the softest sound they can hear)
  • The acoustic reflex threshold (when the stapedius muscle contracts)
    
    In a person with normal hearing, the acoustic reflex typically occurs about 70-90 decibels above their hearing threshold. But in someone with cochlear recruitment, this gap narrows significantly. If the acoustic reflex occurs less than 60 decibels above the hearing threshold, we consider it a positive Metz test, indicating cochlear recruitment and suggesting a problem in the inner ear. The primary advantage of the Metz test is that it's objective: we don't rely on the patient's subjective responses
    
    
• Otoacoustic Emissions (OAEs): These tests can help evaluate the function of the outer hair cells in the cochlea, which are often involved in hyperacusis.
  

• Loudness Discomfort Levels (LDLs): This test measures the decibel levels at which sounds become uncomfortable, helping gauge the degree of sound sensitivity. In hyperacusis patients, LDLs are typically lower than normal.

• Imaging Studies (CT temporal bones typically): If there is suspicion of conditions like superior canal dehiscence or a vestibular disorder, imaging studies can be helpful for confirmation.
  
  
• Questionnaires and Quality-of-Life Assessments: Tools like the Hyperacusis Questionnaire (HQ) may assess the impact of hyperacusis on daily life and mental health

Effective Treatments Options

Managing hyperacusis involves both relieving symptoms and addressing underlying causes: